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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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The North Sea is a major continental basin filled with sediments ranging in age from early Paleozoic to recent. It has been active several times in the past. Since the last
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epoch of activity, extending from the Middle Jurassic until the Early Cretaceous time it has been queiscent and the Central graben has been filled successively by chalks, sandstones, and, finally during most of the Tertiary, by shales or mudstones. The rate of subsidence of the basin, calculated by plotting observed depth in hole versus time, during this quiescent period appears to increase in the later stages. However, when compaction, water depth of deposition, and sediment load are considered, the rate of subsidence of the basement becomes close to linear trending to exponential.
Between 50 and 100% stretching of the Central graben during the last epoch of activity can account for the observed amplitude and rate of subsidence. Such stretching is compatible with the measured heat flow and though there is no actual seismic refraction data across the Central graben this explanation is strongly supported by evidence of a thinner crust under the Viking, Witchground, and Buchan grabens to the north. A geologic model based on stretching which can account for the Jurassic and Early Cretaceous faulting and the general post-mid-Cretaceous saucer-shaped basin is presented. On the basis of this model the thermal maturity and hydrocarbon potential of certain sedimentary horizons in the northern part of the Central graben are examined.
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